The Effect of Ultrasound on the Bioactive Compounds of Essential Oil Extracted from the Peel of Orange Thomson Cultivar

In recent years, the use of citrus peel essential oil as a natural preservative in foods has been widely considered. There are several methods to extract the essence oil of orange peel, one of which is the use of ultrasound. The objective of this study was to evaluate the extraction conditions of essential oil by ultrasound method from the peel of Thompson cultivar using the response surface methodology.

Independent variables included ultrasound intensity, time and process temperature at three levels of 20, 60 and 100%, 5, 10 and 15 min and 25, 35 and 45 ͦ C were studied, respectively. Efficiency of extraction, total phenolic compounds, DPPH and inhibitory of orange peel essential oils against Aspergillus niger fungus were determined.

The optimal conditions for extracting the essential oil of orange peel were sonication intensity 60%, processing time and temperature of 19 min and 35 °C respectively. At this optimum condition, efficiency of extraction, phenolic compounds and DPPH value of the orange peel essential oils were 13.09%, 42.16 mg/100g and 55%, respectively. The experimental values were in a good agreement with the predicted values. Also, at the optimal conditions, the minimum inhibitory concentration (MIC) of the orange peel essential oils was 18.5 mm and potassium sorbate was 18.3 mm. Therefore, orange peel essential oil at a concentration equal to potassium sorbate (1000 mg/ml) has antifungal activity against Aspergillus niger.

The present study revealed that the essential oil of orange peel has a potential source of active ingredients like polyphenols that are well-known for their antioxidant properties. Ultrasound extraction is an effective technique for extraction of these compounds. Also orange peel essential oil can be used in foods instead of chemical and synthetic antioxidants and preservatives.